... possibly because the "Old West" was still around when film companies moved to California in the 1910s, and even by the 1920s memories of it were still clear.
Originally, with film companies based in the east, a background of a western landscape would be constructed and the Western would play out in confined quarters. When the film companies moved to California to escape Edison and to find a place where they could shoot outdoors year round they discovered that the actual cowboys were still around. So many of them - able to rope, shoot, and ride - populated those early westerns with actual ranch hand work drying up.
The episode of course talks about the well known western silent stars - W. S. Hart, Tom Nix, and Harry Carey. But they also talk about how reality would sometimes merge with art. The episode discusses Al Jennings who was first an attorney, then an outlaw, and finally a Western filmmaker. His story is involved so I will point you in the direction of Wikipedia. He lived to be 98, dying in 1961.
Much time is devoted to the making of "The Covered Wagon" in 1923, by director James Cruze. This was a real project of passion for Cruze. He used ordinary westerners for extras, recruited actual Conestoga wagons that were heirlooms in the families that still had them, and blew his budget wide open, but it remains a great epic. This is as close to the definitive documentary on the making of that film you are probably ever going to see, although the film is available on physical media.
Ultimately, the silent Westerns remain truly authentic, because you had actual cowboys and even a few outlaws participating, and the west STILL looked like the old west - even In California - all through the silent period. The coming of sound caused the Western to be unable to be made for a couple of years due to the fact that sound films could not be shot outdoors.
What is missing from this episode? Some of the western stars who didn't make the jump to sound and why. They didn't even have work from 1928 to 1930 when outdoor camera technology improved. Some western stars were illiterate (Jack Hoxie). And then there are those where we wonder - What might have been? That includes Fred Thomson, husband of famous screenwriter Frances Marion, who died of tetanus on Christmas day 1928. He was as big of a Western star as Tom Nix during the 20s, and he died at the very end of the silent era. Would he have made the transition? Had he not, what would he have done instead? This entire paragraph consists of my own thoughts, unexplored by this episode, but I'll give it a break because there is less than an hour to tell the tale of an entire genre.